Problem grabbing parameters using execfile within a class

Question

I have a problem similar to the first problem in this question, which as far as I can see went unanswered.

I have a file "config.py" which contains a lot of parameters to be used by a class (this config.py file will change), however I can't get these to propagate into the class via execfile.

In an example piece of code:

class Class():
    def __init__(self):
        execfile("config.py")
        print x

# config.py
x = "foo"

>>> t = Class()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<stdin>", line 4, in __init__
NameError: global name 'x' is not defined

Any help welcome, or any better methods of retrieving parameters from a file to be used in a class.

Many Thanks.

mouad · Accepted Answer · 2011-06-16T13:47:38.110

I don't get what you're trying to do (but i don't like it, and this is just me) but to fix your problem do (test in python2.6):

class Class():
    def __init__(self):
        execfile('config.py', locals())  # Not recommanded, maybe you want globals().
        print x

But from the doc:

Note

The default locals act as described for function locals() below: modifications to the default locals dictionary should not be attempted. Pass an explicit locals dictionary if you need to see effects of the code on locals after function execfile() returns. execfile() cannot be used reliably to modify a function’s locals.

and about :

Any help welcome, or any better methods of retrieving parameters from a file to be used in a class.

You can use import.

@Jdog: with `globals()` the variable will be set in the global scope and the variable in config.py will be availabe everywhere in your module. Just to make sure that this is what you want :) — mouad, Jun 16 '11 at 13:58

score 1 · Answer 2 · answered Jun 16 '11 at 13:59

Even though it might be convenient to keep configuration settings in a Python file I would recommend against it. I think it opens up a whole set of problems that you don't really want to have do deal with. Anything could be placed in your configuration file, including malicious code.

I would use either the json module or the ConfigParser module to hold my configuration.

If you have trouble choosing between those two I would recommend the json module. Json is a simple yet flexible format for structured data.

Thanks, I'll look in to json. Should be safe enough for the time being as there is only me that will be using the program or have access to it :) — Jdog, Jun 17 '11 at 11:11

Problem grabbing parameters using execfile within a class

2 Answers2